Polygon compensation coupling for chain and sprocket driven systems

ABSTRACT

A polygon compensation coupling system for reducing a polygon effect in a chain driven system is disclosed. The polygon compensation coupling system may include a chain sprocket and a main drive in engagement with the chain sprocket, such that the engagement defines a compensation curve to reduce the polygon effect.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.14/110,070, filed Oct. 4, 2013 which is a 371 U.S. National Stage patentapplication of PCT/US11/37553 filed on May 23, 2011, the disclosure ofwhich is incorporated by reference herein in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure generally relates to chain and sprocket drivensystems and, more particularly, relates to minimizing a polygon effectassociated with chain and sprocket driven systems, such as, passengerconveyor systems.

BACKGROUND OF THE DISCLOSURE

Several types of passenger conveyor systems, such as, escalators, movingwalkways, moving sidewalks, etc. are widely used these days toeffectively transport pedestrian traffic (or other objects) from onelocation to another. Areas of usage of these passenger conveyor systemsoften include airports, hotels, shopping malls, museums, railwaystations and other public buildings. Such passenger conveyor systemstypically have two landings (e.g., a top landing and a bottom landing)that bridge a truss structure. Moving handrails, as well as a pluralityof steps/treads guided by a step chain (also called an escalator chain)in a loop transport the pedestrian traffic between the two landings. Thestep chain can be guided (e.g., driven) by a step chain sprocket. Inparticular, the passenger conveyor systems generally include a drivemodule having a motor and a main shaft, which drives one or more maindrive chain sprockets, which in turn drives the step chain sprocket formoving the plurality of steps in the endless loop.

The interaction of the step chain with the step chain sprocket oftenproduces fluctuations and vibrations. By way of background, a step chainincludes a plurality of discrete step chain links connected together byway of connecting links, such as, a pin and a link plate or a roller,while a sprocket (e.g., the step chain sprocket) includes a profiledwheel having a plurality of engaging teeth for meshing and engaging theconnecting links (or possibly even engaging the step chain links) of thestep chain for moving the step chain as the step chain sprocket rotates.The engagement of the connecting links of the step chain with theengaging teeth of the step chain sprocket causes the step chain tovibrate and fluctuate. These vibrations and fluctuations are oftencalled a polygon effect or a chordal action and not only affect the rideexperience of a user (who typically feels these vibrations andfluctuations aboard the passenger conveyor system), but it also causesundesirable friction between the step chain and the step chain sprocket,thereby reducing the lifespan of those components. Noise generated bythe vibrations resulting from the engagement of the step chain with thestep chain sprocket is another concern.

Therefore, mitigating or compensating the polygon effect is desirable.Several solutions to reduce or otherwise mitigate the polygon effecthave been proposed in the past. Generally speaking, the intensity ofpolygon effect depends upon the velocity (frequency) of the step chainand the amplitude of the step chain pitch−step chain sprocket pitch. Thegreater the step chain pitch, the higher the polygon effect. To reducethe polygon effect, therefore, the pitch of the step chain can bereduced. Thus, one approach of mitigating the polygon effect involvesincreasing the number of step chain links in the step chain (which canreduce the step chain pitch), and/or correspondingly increasing thediameter of the step chain sprocket(s) to increase the number of teeththereon (which may also effectively reduce the step chain pitch). Thistechnique, although effective in improving the riding experience of auser, nonetheless has several disadvantages.

For example, due to the increase in the number of the parts (e.g.,increase in the number of step chain links and other associated parts,such as, rollers, pins, bushings, link plates, etc., of the step chain,and/or a bigger sprocket), the overall cost of the associated systemincreases. Furthermore, the maintenance involved with the upkeep of theincreased number of components goes up as well, and so does the amountof lubricant needed to reduce the increased wear and tear amongst thosecomponents. This increased wear and tear can additionally reduce thelifespan of the step chain and the step chain sprocket. Moreover, theaforementioned approach does not address the noise issue discussedabove, and may in fact increase the noise due to a greater engagement ofthe step chain with the step chain sprocket.

Accordingly, there is a need for an effective solution to compensate thepolygon effect that does not suffer from the disadvantages mentionedabove. Particularly, it would be beneficial if a polygon compensationtechnique were to be developed that improved the riding experience ofthe users without incurring any additional costs associated withincreasing the step chain links or using a bigger step chain sprocket.It would further be beneficial if such a technique were reliable, easyto maintain, increased (or at least did not negatively impact) thelifespan of the step chain and the step chain sprocket (e.g., byreducing wear and tear), and additionally provided a greener approach(by using less lubricant) to solving the polygon effect problem. Itwould additionally be desirable if this technique reduced the noisegenerated by the step chain and the step chain sprocket engagement.

SUMMARY OF THE DISCLOSURE

In accordance with one aspect of the present disclosure, a polygoncompensation coupling system is disclosed. The polygon compensationcoupling system may include a chain sprocket and a main drive. The maindrive may be in engagement with the chain sprocket such that theengagement may define a compensation curve to reduce a polygon effect.

Additionally, the chain sprocket of the polygon compensation couplingsystem may include a plurality of compensation holes, each of theplurality of compensation holes may be approximately equally spacedcircumferentially apart from one another. Furthermore, the main drivemay be engaged to the chain sprocket through each of the plurality ofcompensation holes by a respective axle, such that rotation of the maindrive causes rotation of each of the respective axle within each of theplurality of compensation holes in accordance with the compensationcurve.

Alternatively, the chain sprocket of the passenger conveyor system mayhave a first plurality of engagement surfaces and the main drive mayhave a corresponding number of second plurality of engagement surfacessuch that rollers sliding in the corresponding first and the secondplurality of engagement surfaces of the chain sprocket and the maindrive define a stationary compensation curve.

Additionally, the main drive and the chain sprocket may rotate withnon-constant instantaneous angular velocities, while maintainingconstant average angular velocities, such that linear speed of a chainmay be kept substantially constant.

In accordance with another aspect of the present disclosure, a passengerconveyor system is disclosed. The passenger conveyor system may includea plurality of treads guided by a step chain in an endless loop about astep chain sprocket for transporting objects from one location toanother. The step chain sprocket may include a plurality of compensationholes. The passenger conveyor system may additionally include a maindrive in engagement with the step chain sprocket by a plurality ofaxles, the engagement defined by a compensation curve as the step chainsprocket and the main drive rotate with constant average angularvelocities but non-constant instantaneous angular velocities.

In accordance with yet another aspect of the present disclosure, amethod of reducing a polygon effect in a chain driven system isdisclosed. The method may include providing a chain moving in an endlessloop guided by a chain sprocket and a main drive. The method may furtherinclude engaging the chain sprocket with the main drive and rotating thechain sprocket and the main drive with constant average angularvelocities but non-constant instantaneous angular velocities. The methodmay further include providing a compensation curve to maintain asubstantially constant linear speed of the chain.

Additionally, the method may include providing the chain sprocket with aplurality of compensation holes and connecting the main drive to thechain sprocket through the plurality of compensation holes by way of aplurality of axles. Furthermore, the method may include guiding theplurality of axles within the plurality of compensation holes to definethe compensation curve.

Alternatively, the method may include providing each of the chainsprocket and the main drive with a plurality of engagement surfaces andproviding a stationary compensation curve defined by rollers sliding incorresponding engagement surfaces of the chain sprocket and the maindrive.

Additionally or alternatively, the invention may include one or more ofthe following features separately or in combination:

-   -   wherein a main drive and a chain sprocket are mounted to a main        drive shaft for rotation;    -   wherein a chain sprocket and a main drive rotate with constant        average angular velocity;    -   wherein a chain sprocket and a main drive rotate with        non-constant instantaneous angular velocities;    -   wherein a chain sprocket and a main drive have non-constant        instantaneous angular velocities while maintaining constant        average angular velocities;    -   wherein non-constant instantaneous angular velocities of a main        drive and a chain sprocket causes a linear speed of a chain to        be kept substantially constant;    -   wherein a main drive is a main drive chain sprocket; and/or    -   wherein a main drive is driven substantially directly by way of        gears, axles, and/or motors and the like.

Other advantages and features will be apparent from the followingdetailed description when read in conjunction with the attacheddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the disclosed methods andapparatuses, reference should be made to the embodiments illustrated ingreater detail on the accompanying drawings, wherein:

FIG. 1A shows a simplified schematic diagram of a passenger conveyorsystem, in accordance with at least some embodiments of the presentdisclosure;

FIG. 1B shows a portion of the passenger conveyor system of FIG. 1 ingreater detail;

FIG. 2 shows a front view of a step chain sprocket of the passengerconveyor system of FIG. 1, in accordance with at least some embodimentsof the present disclosure;

FIG. 3 shows a schematic front view of a first embodiment of a polygoncompensation coupling system employed within the passenger conveyorsystem of FIG. 1;

FIG. 4 shows a side view of the polygon compensation coupling system ofFIG. 3;

FIG. 5 shows a Cartesian coordinate system mathematical representationof a step one of determining a compensation curve equation of thepolygon compensation coupling system;

FIG. 6 shows a Cartesian coordinate system mathematical representationof a step two of determining the equation for the compensation curve ofFIG. 5;

FIG. 7 shows an example of the geometry of the compensation curve ofFIGS. 5 and 6;

FIG. 8 is a schematic front view of a second embodiment of the polygoncompensation coupling system of FIG. 3;

FIG. 9 shows a perspective view of a third embodiment of the polygoncompensation coupling system of FIG. 3;

FIG. 10A shows a first schematic front view of the polygon compensationcoupling system of FIG. 9; and

FIG. 10B shows a second schematic front view of the polygon compensationcoupling system of FIG. 9.

While the following detailed description has been given and will beprovided with respect to certain specific embodiments, it is to beunderstood that the scope of the disclosure should not be limited tosuch embodiments, but that the same are provided simply for enablementand best mode purposes. The breadth and spirit of the present disclosureis broader than the embodiments specifically disclosed and encompassedwithin the claims eventually appended hereto.

DETAILED DESCRIPTION OF THE DISCLOSURE

Referring now to FIGS. 1A and 1B, an exemplary passenger conveyor system2 is shown, in accordance with at least some embodiments of the presentdisclosure. Although the passenger conveyor system 2 shown is anescalator, it will be understood that the passenger conveyor system isrepresentative of various types of chain driven mechanisms that engage adrive chain having discrete links engaged with a toothed sprocket.Furthermore, the passenger conveyor system 2 need not always be at anincline as shown. Rather, in at least some embodiments, the passengerconveyor system 2 may be horizontal as in a moving walk, curved, spiralor may define any other commonly employed configuration.

While all of the components of the passenger conveyor system 2 have notbeen shown, a typical passenger conveyor system of the type that may beemployed for purposes of the present disclosure may include a bottomlanding 4 connected to a top landing 6 via a plurality of steps (alsoreferred to herein as treads) 8 and a truss 10. A step chain 12 having aplurality of step chain links 14 may be connected to the plurality oftreads 8 to guide and move those steps in an endless loop via a stepchain sprocket 16 (See FIG. 1B) between the top landing 6 and the bottomlanding 4. As shown in FIG. 1B, the passenger conveyor system 2 mayadditionally include a drive module 18. The drive module 18 may beprovided beneath the top landing 6 and may include a motor 20, which mayat least indirectly drive a main drive shaft 22 having a machine drivechain sprocket 25. The machine drive chain sprocket 25 in turn may drivea main drive chain 21 to which is engaged a main drive chain sprocket24. The main drive chain (MDC) sprocket 24 may engage with, and rotateconcurrently with, the step chain (STC) sprocket 16 to move the stepchain 12. The passenger conveyor system 2 may further include a pair ofmoving handrails 26 (only one of which is shown in FIG. 1A).

Notwithstanding the components of the passenger conveyor system 2described above, it will be understood that several other components,such as, gearbox, brakes, etc., that are commonly employed in passengerconveyor systems are contemplated and considered within the scope of thepresent disclosure. It will also be understood that while several of thecomponents, such as, the machine drive chain sprocket 25 and the maindrive sprocket 24 of the drive module 18 described above are driven bychains, in at least some embodiments, one or more of those componentsmay be driven by belts or other commonly employed mechanisms.Furthermore, in at least some embodiments, the main drive shaft 22 maydirectly drive (by way of belts or chains) the MDC sprocket 24, withoutthe usage of the machine drive chain sprocket 25 and the main drivechain 21. In yet other embodiments, the main drive shaft 22 may directlydrive (by belts or chains) the STC sprocket 16 without the usage of themachine drive chain sprocket 25 or the MDC sprocket 24.

Referring now to FIG. 2, a front view of the step chain (STC) sprocket16 is shown, in accordance with at least some embodiments of the presentdisclosure. As shown, the STC sprocket 16 may be a round (orsubstantially round) disk or wheel and may be mounted to the main driveshaft 22. The STC sprocket 16 may additionally include a plurality ofteeth 30 formed along a circumference thereof, to engage connectinglinks (e.g., in the form of rollers) 32 (See FIG. 3) of the step chain12 as the STC sprocket rotates to move the step chain thereabout.Notwithstanding the fact that in the present embodiment, only three ofthe teeth 30 have been shown in the STC sprocket 16, in otherembodiments, the number of teeth may vary.

Also formed on a front surface of the STC sprocket 16, are threecompensation holes 34. As will be noted, each of the compensation holes34 is not circular, but rather defines an eccentric path 36 for anaxle/roller 38 (shown in phantom in FIG. 2) to follow as the STCsprocket 16 and the MDC sprocket 24 rotate to move the step chain 12. Inso doing, the eccentric path 36 defines a compensation curve 42,described below with respect to FIG. 7, which may serve to reduce thepolygon effect described above. In particular, the compensation curve 42may vary the angular velocity of the STC sprocket 16 in order tomaintain a constant speed (e.g., linear speed) of the step chain 12 asthe step chain engages and moves about the STC sprocket, therebyminimizing (or possibly even completely eliminating) the polygon effect.

With respect to the compensation holes 34, in at least some embodiments,they may be arranged in a triangular configuration 120° apart towards acenter portion of the STC sprocket 16, adjacent to the teeth 30 andabutting the main drive shaft 22. Although in the present embodiment,three compensation holes 34 have been shown, in at least some otherembodiments, the number of compensation holes may vary and the number ofcompensation holes need not correspond to the number of teeth 30 on theSTC sprocket 16. Furthermore, the positioning of those holes may vary aswell and they need not always be positioned adjacent to the teeth 30 ofthe STC sprocket 16 or be separated from one another by a 120°.Additionally, although all of the compensation holes 34 have been shownto have the same geometric shape, in at least some embodiments, one ormore of the compensation holes 42 may have varying radii or shapes otherthan that depicted. The intent of the engagement between the shapedcompensation holes 34 and the axles/rollers 38 is to follow thecompensation curve as defined in the following figures.

Referring now to FIGS. 3 and 4, a polygon compensation coupling system28 is shown, in accordance with at least some embodiments of the presentdisclosure. As shown, the step chain 12 may be engaged with the STCsprocket 16, which in turn may be engaged with the MDC sprocket 24. Inparticular, the STC sprocket 16 may be mounted to the main drive shaft22, as mentioned above. The STC sprocket 16 may additionally besandwiched between two of the MDC sprockets (also referred to herein asMDC rings) 24, one on either side of the STC sprocket, as shown in FIG.4. The two MDC sprockets 24 may be connected to one another and held inposition about the main drive shaft 22 and relative to the STC sprocket16 by way of the axles (also referred to herein as rollers) 38 andplates 40. Particularly, each of the MDC sprockets 24 may be formed witha set of three corresponding holes (not visible) such that each of theaxles 38 may be inserted through one of the two MDC sprockets 24,through one of the compensation holes 34 and out through the other ofthe two MDC sprockets. The axles 38 may be held in position by theplates 40. Other mechanisms to secure and hold the axles 38 in positionmay be employed in alternate embodiments.

Furthermore, the axles 38 may connect the two MDC sprockets 24 in amanner such that as the MDC sprockets and the STC sprocket 16 rotate,the axles 38 roll/guide along and follow the eccentric path 36 of thecompensation holes 34 to define the compensation curve 42. The geometryof the compensation curve 42 is shown in greater detail in FIG. 7. Thecompensation curve 42 may also be explained mathematically, as shown inFIGS. 5 and 6. By virtue of providing the compensation holes 34 in theSTC sprocket 16 and rolling the axles 38 of the MDC sprockets 24 withinthe compensation holes to define the compensation curve 42, both the STCsprocket and the MDC sprocket made be turned a 360° in the same amountof time. Particularly, the MDC sprockets 24 may be made to rotate at aconstant average angular velocity and the STC sprocket 16 may be made torotate with the same average angular velocity but with a different(e.g., non-constant) relative angular velocity (i.e., different ornon-constant instantaneous angular velocity) at any given point in therotation, such that the difference in the angular velocities ensuresthat the step chain 12 is kept moving at a constant speed to compensate(or possibly even completely eliminate) the polygon effect. In otherwords, the relative difference in the instantaneous angular velocitiesof the STC sprocket 16 and the MDC sprocket 24 counteracts the polygoneffect by a certain compensation curve (e.g., the compensation curve42), which reduces or eliminates the polygon effect.

Turning now to FIGS. 5 and 6, a mathematical representation (e.g.,equation) of the compensation curve 42 is shown, in accordance with atleast some embodiments of the present disclosure. In particular, FIG. 5shows a first step (e.g., a frame of reference) for determining anequation for the compensation curve 42, while FIG. 6 shows a second stepin the determination thereof. Referring specifically to FIG. 5, first, aposition and a velocity of a point one (1) with a coordinate u may bedetermined for every step chain link 14 of the step chain 12, asspecified below. In the equations, p may refer to a radius of a circleequal to a pitch of a single step chain link 14, while r may refer to aradius of a circle equal to a pitch of the STC sprocket 16 and thecrossing point one (1) may be the point of intersection of the circles pand r, and may have coordinates (x,y), in dependence of u (e.g., x(u),y(u)).

Thus, the position of point one (1) (x(u), y(u)) in a Cartesiancoordinate system may be determined as follows:

Circle one equation:

(x−u)²+(y−t)² =p ²  (1)

Circle two equation:

x ² +y ² =r ²  (2)

Inserting (2) in (1):

a=((u ² +r ² +t ² −p ²)/2)  (3)

resulting in a common quadratic solution for x(u):

$\begin{matrix}{x_{1} = \frac{{au} - {{Sqrt}\left\lbrack {{- \left( {a^{2}*t^{2}} \right)} + {r^{2}*t^{4}} + {r^{2}*t^{2}*u^{2}}} \right\rbrack}}{t^{2} + u^{2}}} & \left( {4a} \right) \\{x_{2} = \frac{{au} + {{Sqrt}\left\lbrack {{- \left( {a^{2}*t^{2}} \right)} + {r^{2}*t^{4}} + {r^{2}*t^{2}*u^{2}}} \right\rbrack}}{t^{2} + u^{2}}} & \left( {4b} \right)\end{matrix}$

For a simplified specific case when

t=r  (5)

(4a) can be transformed to

x=((u*(−p ²+2*r ² +u ²))/2+Sqrt[r ⁶ +r ⁴ +u ²−(r ²*(−p ²+2*r ² +u²)²)/4])/(r ² +u ²)   (6)

With the pitch-radius correlation in the STC sprocket 16 with z teeth, asegment angle w may be expressed as

w=p/z  (7)

and the radius r may be expressed by

r=p/(2*Sin [w])  (8)

for the constant term Sin [w]

Sin [w]=k  (9)

Thus, equation (8) may be written as

p=2*r*k  (10)

Inserting equation (10) in equation (6), x(u) may be written as follows:

x(u)=((u*(2*r ²−4*k ² *r ² +u ²))/2+Sqrt[r ⁶ +r ⁴ *u ²−(r ²*(2*r ²−4*k ²*r ² +u ²)²)/4])/(r ² +u ²)  (11)

from equation (1):

y=t−Sqrt[p ²−(x−u)²]  (12)

Inserting equations (5) and (10) in equation, (12):

y=r−Sqrt[(2*r*k)²−(x−u)²]  (13)

and inserting equation (11) in equation (13) results in:

y(u)=r−Sqrt[(2*r*k)²−((−u((u*(2*r ²−4*k ² *r ² +u ²))/2+Sqrt[r ⁶ +r ⁴ *u²−(r ²*(2*r ²−4*k ² *r ² +u ²)²)/4])/(r ² +u ²)))²]  (14)

Subsequent to determining the position (coordinates of x(u), y(u))) ofpoint one (1), the velocity of point one (1) in the x and the ydirections may be determined as follows:

Differentiating equation (11) with respect to u results in the velocityof point one (1) in an x-direction:

x′(u)=(u ²+(2*r ²−4*k ² *r ² +u ²)/2+(2*r ⁴ *u−r ² *u*(2*r ²−4*k ² *r ²+u ²))/(2*Sqrt[r ⁶ +r ⁴ *u ²−(r ²*(2*r ²−4*k ² *r ² +u ²)²)/4]))/(r ² +u²)−(2*u*((u*(2*r ²−4*k ² *r ² +u ²))/2+Sqrt[r ⁶ +r ⁴ *u ²−(r ²*(2*r²−4*k ² *r ² +u ²)²)/4]))/(r ² +u ²)²  (15)

while differentiating equation (14) with respect to u results in thevelocity of point one (1) in a y-direction:

y′(u)=((−1+(u ²+(2*r ²−4*k ² *r ² +u ²)/2+(2*r ⁴ *u−r ² *u*(2*r ²−4*k ²*r ² +u ²))/(2*Sqrt[r ⁶ +r ⁴ *u ²−(r ²*(2*r ²−4*k ² *r ² +u ²)²)/4]))/(r² +u ²)−(2*u*((u*(2*r ²−4*k ² *r ² +u ²))/2+Sqrt[r ⁶ +r ⁴ *u ²−(r ²*(2*r²−4*k ² *r ² +u ²)²)/4]))/(r ² +u ²)²)*(−u+((u*(2*r ²−4*k ² *r ² +u²))/2+Sqrt[r ⁶ +r ⁴ *u ²−(r ²*(2*r ²−4*k ² *r ² +u ²)²)/4]))/(r ² +u²)))/Sqrt[4*k ² *r ²−(−u+((u*(2*r ²−4*k ² *r ² +u ²))/2+Sqrt[r ⁶ +r ⁴ *u²−(r ²*(2*r ²−4*k ² *r ² +u ²)²)/4])/(r ² +u ²))²]  (16)

and the absolute value of the velocity of point one (1) may be given by:

v(u)=Sqrt[x′(u)² +y′(u)²]  (17)

From the velocity of point one (1), the acceleration of point one (1)may be determined by further differentiating the equations (15) and(16), with respect to u to obtain acceleration in the x- and they-directions. Thus, differentiating equation (15) gives the accelerationof point one (1) in the x-direction as follows:

x″(u)=(6*u−((16*k ² *r ⁴ *u−4*r ² *u ³)*(8*k ² *r ⁴ *u−2*r ² *u³))/(2*(−16*k ⁴ *r ⁶ −r ² *u ⁴+8*k ² *r ⁴*(2*r ² +u ²))̂(3/2))+(8*k ² *r⁴−6*r ² *u ²)/Sqrt[−16*k ⁴ *r ⁶ −r ² *u ⁴+8*k ² *r ⁴*(2*r ² +u²)])/(2*(r ² +u ²))−(u*(2*r ²−4*k ² *r ²+3*u ²+(8*k ² *r ⁴ *u−2*r ² *u³)/Sqrt[−16*k ⁴ *r ⁶ −r ² *u ⁴+8*k ² *r ⁴*(2*r ²+²)]))/(r ² +u²)̂2−(u*((2−4*k ²)*r ²+3*u ²+(8*k ² *r ⁴ *u−2*r ² *u ³)/Sqrt[−16*k ⁴ *r ⁶−r ² *u ⁴+8*k ² *r ⁴*(2*r ² +u ²)]))/(r ² +u ²)̂2+(4*u ²*((2−4*k ²)*r ²*u+u ³+Sqrt[−16*k ⁴ *r ⁶ −r ² *u ⁴+8*k ² *r ⁴*(2*r ² +u ²)]))/(r ² +u²)̂3−((2−4*k ²)*r ² *u+u ³+Sqrt[−16*k ⁴ *r ⁶ −r ² *u ⁴+8*k ² *r ⁴*(2*r ²+u ²)])/(r ² +u ²)̂2  (18)

and differentiating equation (16) gives the velocity of point one (1) inthe y-direction as follows:

y″(u)=((−4*k ² *r ² *u−u ³+Sqrt[−16*k ⁴ *r ⁶ −r ² *u ⁴+8*k ² *r ⁴*(2*r ²+u ²)])*((6*u−((16*k ² *r ⁴ *u−4*r ² *u ³)*(8*k ² *r ⁴ *u−2*r ² *u³))/(2*(−16*k ⁴ *r ⁶ r ² *u ⁴+8*k ² *r ⁴*(2*r ² +u ²))̂(3/2))+(8*k ² *r⁴−6*r ² *u ²)/Sqrt[−16*k ⁴ *r ⁶ −r ² *u ⁴+8*k ² *r ⁴*(2*r ² +u²)])/(2*(r ² +u ²))−(u*(2*r ²−4*k ² *r ²+3*u ²+(8*k ² *r ⁴ *u−2*r ² *u³)/Sqrt[−16*k ⁴ *r ⁶ −r ² *u ⁴+8*k ² *r ⁴*(2*r ² +u ²)]))/(r ² +u²)̂2−(u*((2−4*k ²)*r ²+3*u ²+(8*k ² *r ⁴ *u−2*r ² *u ³)/Sqrt[−16*k ⁴ *r ⁶−r ² *u ⁴+8*k ² *r ⁴*(2*r ² +u ²)]))/(r ² +u ²)̂2+(4*u ²*((2−4*k ²)*r ²*u+u ³+Sqrt[−16*k ⁴ *r ⁶ −r ² *u ⁴+8*k ² *r ⁴*(2*r ²+²)]))/(r²+²)̂3−((2−4*k ²)*r ² *u+u ³+Sqrt[−16*k ⁴ *r ⁶ −r ² *u ⁴+8*k ² *r ⁴*(2*r² +u ²)])/(r ² +u ²)̂2))/(2*(r ² +u ²)*Sqrt[4*k ² *r ²−(4*k ² *r ² *u+u³−Sqrt[−16*k ⁴ *r ⁶ −r ² *u ⁴+8*k ² *r ⁴*(2*r ² +u ²)])̂2/(4*(r ² +u²)̂2)])+((−4*k ² *r ²−3*u ²+(8*k ² *r ⁴ *u−2*r ² *u ³)/Sqrt[−16*k ⁴ *r ⁶−r ² *u ⁴+8*k ² *r ⁴*(2*r ² +u ²)])*(−1+(2*r ²−4*k ² *r ²+3*u ²+(8*k ²*r ⁴ *u−2*r ² *u ³)/Sqrt[−16*k ⁴ *r ⁶ r ² *u ⁴+8*k ² *r ⁴*(2*r ² +u²)])/(2*(r ² +u ²))−(u*((2−4*k ²)*r ² *u+u ³+Sqrt[−16*k ⁴ *r ⁶ −r ² *u⁴+8*k ² *r ⁴*(2*r ² +u ²)]))/(r ² +u ²)̂2))/(2*(r ² +u ²)*Sqrt[4*k ² *r²−(4*k ² *r ² *u+u ³−Sqrt[−16*k ⁴ *r ⁶ −r ² *u ⁴+8*k ² *r ⁴*(2*r ² +u²)])̂2/(4*(r ² +u ²)̂2)])−(u*(−4*k ² *r ² *u−u ³+Sqrt[−16*k ⁴ *r ⁶ −r ² *u⁴+8*k ² *r ⁴*(2*r ² +u ²)])*(−1+(2*r ²−4*k ² *r ²+3*u ²+(8*k ² *r ⁴*u−2*r ² *u ³)/Sqrt[−16*k ⁴ *r ⁶ −r ² *u ⁴+8*k ² *r ⁴*(2*r ²+²)])/(2*(r² +u ²))−(u*((2−4*k ²)*r ² *u+u ³+Sqrt[−16*k ⁴ *r ⁶ −r ² *u ⁴+8*k ² *r⁴*(2*r ² +u ²)]))/(r ² +u ²)̂2))/((r ² +u ²)̂2*Sqrt[4*k ² *r ²−(4*k ² *r ²*u+u ³−Sqrt[−16*k ⁴ *r ⁶ −r ² *u ⁴+8*k ² *r ⁴*(2*r ² +u ²)])̂2/(4*(r ² +u²)̂2)])−((4*k ² *r ² *u+u ³−Sqrt[−16*k ⁴ *r ⁶ −r ² *u ⁴+8*k ² *r ⁴*(2*r ²+u ²)])̂2*(−32*k ⁴ *r ⁶ *u+u ²*(2*r ⁴ *u+3*r ²*Sqrt[−16*k ⁴ *r ⁶ −r ² *u⁴+8*k ² *r ⁴*(2*r ² +u ²)]+u ²*Sqrt[⁻16*k ⁴ *r ⁶ −r ² *u ⁴+8*k ² *r⁴*(2*r ² +u ²)])+4*k ²*(6*r ⁶ *u−r ² *u ²*Sqrt[−16*k ⁴ *r ⁶ −r ² *u⁴+8*k ² *r ⁴*(2*r ² +u ²)]+r ⁴*(2*u ³+Sqrt[−16*k ⁴ *r ⁶ −r ² *u ⁴+8*k ²*r ⁴*(2*r ² +u ²)])))̂2)/(2*r ²*(r ² +u ²)̂6*16*k ⁴ *r ⁴ +u ⁴−8*k ² *r²*(2*r ² +u ²))*((16*k ⁴*(r ⁶ −r ⁴ *u ²)+8*k ² *r ² *u*(3*r ² *u+u³+Sqrt[−16*k ⁴ *r ⁶ −r ² *u ⁴+8*k ² *r ⁴*(2*r ² +u ²)])+u ³*(r ² *u−u³+2*Sqrt[−16*k ⁴ *r ⁶ −r ² *u ⁴+8*k ² *r ⁴*(2*r ² +u ²)]))/(r ² +u²)̂2)̂(3/2))  (19)

and

a=Sqrt[x ² +y ²]  (20)

Subsequent to determining the position, velocity and acceleration of thepoint one (1) with respect to u, the position of a point two (2) locatedon the MDC sprocket 24 for every value of u projected on the STCsprocket 16 may be determined, as shown in FIG. 6, to obtain an equationfor the compensation curve 42 on the STC sprocket. In particular, theSTC sprocket 16 may turn with an angular velocity of dφ/dt and theacceleration dφ/dt², and the compensation curve 42 may be determined bythe curve of the point two (2), which is located on the MDC sprocket 24turning with a constant angular velocity of dθ/dt relative to the STCsprocket. The coordinates of the point two (2) may be represented as (m,n) and the compensation curve 42 may be expressed as (m(u), n(u)).Furthermore, the point two (2) may also refer to the point of engagementof the axles 38 of the MDC sprocket 24 with the compensation holes 34 onthe STC sprocket 16.

A line connecting the points one (1) and two (2) may be expressed asfollows:

b=Sqrt[(x _(1a) −x ₂)²+(y _(1a) −y ₂)²]  (21)

where x_(1a), y_(1a) may be implicitly resolved from equations (11) and(14) and a different radius (a instead of r) may change the positioncoordinates as follows:

x _(1a)=(a/r)*x ₁  (22)

y _(1a)=(a/r)*y ₁  (23)

with

θ(u)=2p/z*((p+u)/p)  (24)

So, the absolute x position of point two (2) may be written as follows:

x ₂ =a*Sin [θ(u)]−e  (25)

and the absolute y position of point two (2) may be written as follows:

y ₂ =a*Cos [θ(u)]  (26)

The relative coordinate m of point two (2) on the STC sprocket 16 may bespecified as:

m(u)=−b*Sin [γ]=−b*Sin [p/2−θ(u)]  (27)

and the relative coordinate n of point two (2) on the STC sprocket 16may be specified as:

n(u)=−b*Cos [γ]=−b*Cos [p/2−θ(u)]  (28)

Thus, the compensation curve 42 may be specified by the point two (2)and equations (27) and (28).

An example 44 of the compensation curve 42 is shown in FIG. 7. Inparticular, the example 44 is created by the point two (2), describedabove, according to the equations (27) and (28) for an STC sprockethaving five (5) teeth. Notwithstanding the fact that the present example44 relates to an STC sprocket with five (5) teeth, a similarcompensation curve may be expressed for the STC sprocket 16 having anynumber of teeth (e.g., the teeth 30).

When both the STC sprocket 16 and the MDC sprocket 24 rotate in the samedirection with a constant angular velocity (e.g., the same averageangular velocity), the compensation curve 42 may be described by ageometric shape, called a compensation circle (or geometric circle),having a radius “e” (See FIG. 7). This compensation circle may be usedas a reference to ascertain the quality of the compensation curve 42. Inparticular, the less the compensation curve 42 deviates from thegeometric circle (e.g., no sharp corners, sharp loops or self crossings)and amplitude (deviation), the smoother is the compensation curve.Deviations from the geometric circle are what compensate for the polygoneffect.

In at least some embodiments, the polygon compensation coupling system28 described above may effectively compensate the polygon effect in thepassenger line (e.g., the side facing the passengers) of the passengerconveyor system 2, but may not compensate the polygon effect effectivelyin the return line (e.g., the side facing away from the passengers afterturning 180° about the STC and the MDC sprockets 16 and 24,respectively) thereof. Accordingly, to effectively compensate thepolygon effect in the return line, either an “open” link in which forone STC pitch length, the STC sprocket 16 is not guided and an STC jointbetween two links rotates freely or by revolving the moving joints in acurve that the STC links have to follow in the track (e.g., thetransition arcs in escalators), may be provided at an “outlet” to thereturn line at the STC sprocket 16. Furthermore, in addition to thepolygon effect experienced by the passenger and the return lines,polygon effect can occur during deviations from a linear track of theSTC sprocket 16 and may be dependent upon the shape and the location ofthe track deviation, the turning direction of the step chain 12, thepitch thereof and frequency of the step chain velocity changes.

Thus, in order to compensate for the polygon effect in the passengerline and the return line as well as to account for other deviations froma linear track, the polygon compensation coupling system 28 may bepositioned at the apex of the arc. For example, when turning the stepchain 12 with a constant speed of 180° in a circle return track, thecompensation curve 42 may be defined at the apex of the arc bow (at90°), which deviates only slightly from the geometry of the compensationcircle described above, is symmetric to linear track lines and works tocompensate the polygon effect in both STC drive directions (e.g., thepassenger line and the return line) of the STC sprocket 24. Thus, an STCsprocket 24 having a pitch of 135.46 millimeters and turning 180° degreein a circle of 190 millimeters diameter may define a compensation curve42 at the apex which deviates about 4 millimeters in diametric directionand is very smooth, thereby effectively compensating for the polygoneffect.

Referring now to FIG. 8, a schematic representation of a secondembodiment of the polygon compensation coupling system 28 is shown as28′, in accordance with at least some embodiments of the presentdisclosure. To the extent that the polygon compensation coupling system28′ is substantially similar to the polygon compensation coupling system28, only the differences between the two will be described here, forconciseness of expression. As shown, similar to the polygon compensationcoupling system 28, the polygon compensation coupling system 28′ mayinclude the step chain 12 having the plurality of step chain links 14and connecting links 32 that engage with the teeth 30 of the STCsprocket 16 as the step chain moves about the rotating STC sprocket. TheSTC sprocket 16 also has the three compensation holes 34, which definethe compensation curve 42. In contrast to the polygon compensationcoupling system 28 in which the MDC sprockets 24 are shown to becircular (or substantially circular), the polygon compensation couplingsystem 28′ employs MDC sprockets 24′ that are triangular (orsubstantially triangular) in shape and that may be driven substantiallydirectly by way of gears, axles, motors and the like.

Although only one MDC sprocket 24′ is visible in FIG. 8, it will beunderstood that two of the MDC sprockets 24′ connected together may beemployed as discussed above with respect to the MDC sprocket 24.Furthermore, the MDC sprockets 24′ may operate and functionsubstantially similarly to the MDC sprockets 24 in that the MDCsprockets 24′ may employ the axles/rollers 38 and plates 40 (notvisible) to engage the compensation holes 34 to move the STC sprocket 16in accordance with the defined compensation curve 42. The compensationcurve 42 may be expressed by the equations (27) and (28) derived above.

It will also be understood that the MDC sprockets 24 and 24′ are merelytwo examples of the kinds of MDC sprockets that may be employed forpurposes of this disclosure. In other embodiments, several differentconfigurations of the MDC sprocket that permit engagement with the STCsprocket 16 and definition of the compensation curve 42 therewith asdescribed above, may be employed and are considered within the scope ofthe present disclosure. Furthermore, in at least some embodiments, theMDC sprockets 24 need not be employed at all. Rather, the engagementbetween the MDC sprockets 24 and the STC sprocket 16 may be definedbetween the belt or chain driven machine drive chain sprocket 25 (SeeFIG. 1B) and the STC sprocket 16 such that the engagement between themachine drive chain sprocket and the STC sprocket defines thecompensation curve 42. In alternate embodiments, the STC sprocket 16 maybe driven directly by the main drive shaft 22 by way of belts and/orchains to define the compensation curve 42.

Turning now to FIGS. 9 and 10A-10B, a third embodiment of the polygoncompensation coupling system 28 is shown as 28″, in accordance with atleast some embodiments of the present disclosure. In contrast to thepolygon compensation coupling systems 28 and 28′, the polygoncompensation coupling system 28″ employs a stationary plate 50 having acircumference that is defined by the determined compensation curve 42above, as well as engagement surfaces (e.g., linear slots) 51 in the STCsprocket 16 and corresponding engagement surfaces (e.g., linear slots)52 in the MDC sprockets 24 (only the linear slots in the MDC sprocketare visible in FIG. 9), all of which may be mounted to center around acommon midpoint 54. The MDC sprocket 24 may be connected to the STCsprocket 16 by a way of a system fixation 56.

By virtue of the compensation curve 42 being fixed, it drives anengagement point 58 in a manner that the step chain 12 maintains asubstantially constant linear speed when the MDC sprocket 24 and the STCsprocket 16 are rotated with the same (e.g., constant) average angularvelocity but with different (e.g., non-constant) instantaneous angularvelocities. In particular, the axles/rollers 38, or other low-frictionelements, engage the surface of the stationary plate 50 (as shown moreclearly in FIG. 10B) and slide in the linear slots 51 and 52 such thatdifferent angular motion of the STC and the MDC sprockets 16 and 24,respectively, is driven by the dynamic radial position of the rollersand the different angles of the linear slots. Specifically, the linearslots 51 and 52 of the STC sprocket 16 and the MDC sprocket 24,respectively, cross at a certain angle. This angle arrangement may pressa compensation element midpoint, which may then be embodied in themovement of the rollers/axles 38, and onto the surface of thecompensation curve 42 (going inside towards the center) of the fixedcompensation part (e.g., the stationary plate 50). Alternatively,depending upon the angle described above, the compensation elementmidpoint may be pressed onto an opposite side of the compensation curve42 (going outside), which in turn may result in a compensation hole(negative part of the shown fixed compensation part 50).

It will be understood that several other geometries for the linear slots51 and 52 may be employed (e.g., arcs) and that the location and theposition of those slots also can be relatively varied as well.Furthermore, in at least some embodiments, the compensation curve 42 maybe determined by running the STC sprocket 16 and the MDC sprocket 24 ata constant speed for the specific geometry of the linear slots 51 and 52and, determining the fixed compensation curve 42 for that speed. In suchcases, the compensation curve 42 may be defined by differentialequations, which may be derived in a manner similar to that describedabove.

Notwithstanding the fact that the engagement surfaces described aboveare linear slots 51 and 52, in other embodiments, the linear slots maybe replaced by other configurations that permit definition of thecompensation curve 42 (e.g., the fixed compensation curve), describedabove. Furthermore, although the polygon compensation coupling system 28has been described above with respect to the passenger conveyor system2, it will be understood that the teachings of the present disclosureare considered applicable to any chain and sprocket driven systems,which experience the polygon effect and to reduce the polygon effectthereof.

INDUSTRIAL APPLICABILITY

In general, the present disclosure sets forth a polygon compensationcoupling system for minimizing (or possibly even completely eliminating)a polygon effect encountered by chain driven systems, such as, passengerconveyor systems. In particular, in some embodiments, the polygoncompensation coupling system involves providing an STC sprocket withcompensation holes and engaging at least one MDC sprocket with the STCsprocket by way of axles or rollers, such that the as the STC sprocketand the MDC sprocket rotate, the axles or rollers rotate within thecompensation holes to define a compensation curve. In other embodiments,the polygon compensation coupling system involves providing both the STCsprocket and the MDC sprocket with linear slots that follow a fixedcompensation curve provided by a stationary plate having thecircumference of the desired compensation curve.

By virtue of defining the compensation curve, the STC sprocket may berotated with changing angular velocities such that a constant linearspeed of the step chain may be maintained as it moves about the rotatingSTC sprocket. Thus, the polygon effect, which stems from the relativespeed differentials of the moving step chain having discrete linksengaging a toothed sprocket, may be reduced (or possibly completelyeliminated) insofar as the speed of the step chain may now be continuousand substantially constant. The substantially constant speed of the stepchain may additionally be ensured by rotating the MDC sprocket and theSTC sprocket with a constant average angular velocity but non-constantinstantaneous angular velocities (as a result of the compensationcurve). Thus, by reducing the polygon effect, the riding experience of apassenger may be enhanced.

Furthermore, the polygon compensation coupling system provides amechanism for reducing the polygon effect without reducing the pitch ofthe step chain (requiring greater number of step chain links), as taughtby conventional polygon effect reducing solutions, described above.Accordingly, the higher cost associated with the step chain and the STCsprocket (stemming from increased number of parts, increased maintenanceand shorter life span) of traditional solutions may also be minimized.Thus, the polygon compensation coupling of the present disclosure notonly ensures a longer lifespan and a cost reduction of the step chainand the STC sprocket, it also provides a greener approach to reducingthe polygon effect due to fewer joints requiring lesser lubricant and anoise-free operation. Additionally, the polygon compensation couplingmechanism is reliable, robust and easily maintainable.

While only certain embodiments have been set forth, alternatives andmodifications will be apparent from the above description to thoseskilled in the art. These and other alternatives are consideredequivalents and within the spirit and scope of this disclosure and theappended claims.

What is claimed is:
 1. A polygon compensation coupling system, thesystem comprising: a chain sprocket; and a main drive chain sprocket inengagement with the chain sprocket; wherein the chain sprocket has afirst engagement surface and the main drive chain sprocket has acorresponding second engagement surface; and a coupling element in thefirst engagement surface and the second engagement surface to define astationary compensation curve to reduce a polygon effect.
 2. The polygoncompensation coupling system of claim 1 wherein the coupling element isa roller.
 3. The polygon compensation coupling system of claim 1,wherein the main drive chain sprocket and the chain sprocket are mountedto a main drive shaft for rotation.
 4. The polygon compensation couplingsystem of claim 1, wherein the chain sprocket and the main drive chainsprocket rotate with constant average angular velocity.
 5. The polygoncompensation coupling system of claim 1, wherein the chain sprocket andthe main drive chain sprocket rotate with non-constant instantaneousangular velocities.
 6. The polygon compensation coupling system of claim1, wherein the chain sprocket and the main drive chain sprocket havenon-constant instantaneous angular velocities while maintaining constantaverage angular velocities.
 7. The polygon compensation coupling systemof claim 6, wherein the non-constant instantaneous angular velocities ofthe main drive chain sprocket and the chain sprocket causes a linearspeed of a chain to be kept substantially constant.
 8. The polygoncompensation coupling system of claim 1, wherein each of the first andthe second plurality of engagement surfaces are linear slots.
 9. Thepolygon compensation coupling system of claim 1, wherein the main drivechain sprocket is driven substantially directly by way of gears, axles,and/or motors.
 10. A passenger conveyor system, the system comprising: aplurality of treads guided by a step chain in an endless loop about astep chain sprocket for transporting objects from one location toanother; and a main drive chain sprocket in engagement with the chainsprocket; wherein the chain sprocket has a first engagement surface andthe main drive chain sprocket has a corresponding second engagementsurface; and a coupling element in the first engagement surface and thesecond engagement surface to define a stationary compensation curve toreduce a polygon effect.
 11. The passenger conveyor system of claim 12wherein the coupling element is a roller.
 12. The passenger conveyorsystem of claim 10, wherein the step chain moves with a substantiallyconstant linear speed.
 13. The passenger conveyor system of claim 10,wherein the main drive chain sprocket comprises a first main drivesprocket and a second main drive sprocket, the first and the second maindrive chain sprockets sandwiching the step chain sprocket.
 14. Thepolygon compensation coupling system of claim 10, wherein each of thefirst and the second plurality of engagement surfaces are linear slots.15. A method of reducing a polygon effect in a chain driven system, themethod comprising: providing a chain driven by a chain sprocket and amain drive chain sprocket; engaging the chain sprocket with the maindrive chain sprocket; rotating the chain sprocket and the main drivechain sprocket with constant average angular velocities but non-constantinstantaneous angular velocities; and providing a compensation curve tomaintain a substantially constant linear speed of the chain; whereinproviding the chain sprocket and the main drive chain sprocket comprisesproviding each of the chain sprocket and the main drive chain sprocketwith a plurality of engagement surfaces and providing the compensationcurve comprises providing a stationary curve in which a coupling elementslides in corresponding engagement surfaces of the chain sprocket andthe main drive chain sprocket.